CN109152898B - Apparatus and method for controlling ventilatory assist - Google Patents

Abstract

The present application relates to an apparatus and method for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator, which during the patient's assisted breathing measures the inspiratory volume V _Assist produced by both the patient and the mechanical ventilator, which is Ventilation with the inspiratory volume V provided by the mechanical _ventilator and the inspiratory assist pressure P generated by the mechanical _ventilator . A first relationship between pressure _Pventilation and volume _Vassist and a second relationship between pressure _Pventilation and volume _Vventilation are calculated. For multiple volumes _Vventilation and _Vassist , the first and second relationships are used to determine the ratio between pressure _{Pventilation at volume Vventilation and} pressure _Pventilation at volume _Vassistance , where volume _Vventilation equals volume _Vassistance . The value of _Pventilation is multiplied by the corresponding calculated ratio to calculate a third relationship between _predicted inspiratory pressure Ppredicted and volume _Vassist . The mechanical ventilator is responsive to the third relationship to control the level of ventilatory assistance.

Description

Apparatus and method for controlling ventilatory assist

Technical Field

The present disclosure relates to devices and methods for controlling the level of ventilatory assist applied to a patient by a mechanical ventilator.

Background

In patients with acute respiratory failure who are actively engaged in inspiration while receiving mechanical ventilatory assist, mechanical ventilatory assist is synchronized with forced inspiration. In addition, the respiratory function and respiratory load of the patient are evaluated to adequately adjust the mechanical ventilationAnd (4) assisting. Traditionally, the determination of the mechanical properties of the patient's respiratory system is made during periods of inactivity of the patient's respiratory muscles (e.g., caused by deep sedation and over-ventilation or paralysis), allowing a mechanical ventilator to apply pressure to the patient's respiratory system to inflate the patient's lungs without the impetus of the respiratory muscles. The data obtained may be represented as a pressure/volume curve showing the pressure required to inflate the patient's respiratory system. The pressure/volume curve may be used to describe a mechanical property of the patient's respiratory system, such as compliance (e.g., ml/cmH)₂O) or elastic (e.g. cmH)₂O/ml) and resistance (cmH)₂O/ml/s). Furthermore, the shape of the pressure/volume curve provides information about the inflection points associated with the patient lung recruitment step during the inspiratory phase.

Measuring respiratory mechanics introduces errors in patients actively involved in mechanical ventilation of inspiration because the inspiratory volume generated by the patient appears in the volume measurement, whereas the patient's pressure is not available unless a pressure sensor (e.g., an esophageal catheter pressure sensor) is introduced into the patient's respiratory system to measure lung distension pressure; however, this measurement does not include the patient's effort/force to dilate the chest wall (i.e., the patient's ribs and abdominal cavity). Thus, without pressure measurement by the patient, the greater the inspiratory volume generated by the patient himself, the greater the error in the measured pressure/volume curve.

The neural activation of the patient's respiratory muscles reflects the force exerted by these muscles. Thus, if two non-assisted breaths (without mechanical ventilation) have the same neural activation, they should provide the same inspiratory volume (no inspiratory pressure). If mechanical ventilation is applied to one of two breaths with the same neural activation, the assisted breath will provide inspiratory pressure (generated by the mechanical ventilator) and its inspiratory volume will increase compared to the non-assisted breath. Given that two breaths have the same neural activation, it can be assumed that the forces of expanding the patient's respiratory system and inflating the lungs during the two breaths are similar. It should be noted, however, that some effect on force occurs during assisted breathing because changes in lung volume affect muscle length/tension and increased flow assistance affects the force/velocity relationship.

With neural activation, using for example the electrical activity of the diaphragm (EAdi), which is the main respiratory muscle, it is necessary to adjust/normalize the pressure/volume curve by eliminating the patient's effort and inspiratory volume production (observed during non-assisted breathing) from assisted breathing (patient + ventilator inspiratory volume but ventilator-generated inspiratory pressure only), in order to achieve: 1) a reliable pressure/volume curve or relationship to describe the patient's respiratory system, and 2) to determine the mechanical pressure and EAdi required to inflate the patient's respiratory system to a given inspiratory volume. The present disclosure is directed to a controller for a mechanical ventilator having such data.

Disclosure of Invention

As a solution and according to a first aspect, the present disclosure provides a method for controlling a level of ventilatory assist applied to a patient by a mechanical ventilator, comprising (a) measuring an inspiratory volume V produced by both the patient and the mechanical ventilator during assisted breathing of the patient_{Assistance of}Inspiratory volume V provided by mechanical ventilator_VentilationAnd an inspiratory assist pressure P generated by the mechanical ventilator_Ventilation(ii) a (b) Calculating the pressure P_VentilationAnd volume V_{Assistance of}A first relationship therebetween; (c) calculating the pressure P_VentilationAnd volume V_VentilationA second relationship therebetween; (d) for a plurality of volumes V_VentilationAnd V_{Assistance of}Calculating the volume V using the first and second relationships_VentilationPressure P of_VentilationWith volume V_{Assistance of}Pressure P of_VentilationIn which volume V_VentilationEqual to volume V_{Assistance of}(ii) a (e) Will P_VentilationIs multiplied by the corresponding calculated ratio to calculate the predicted suction pressure P_PredictionAnd volume V_{Assistance of}A third relationship therebetween; (f) the mechanical ventilator is controlled using a third relationship to control the level of ventilatory assist.

According to a second aspect, there is provided an apparatus for controlling the level of ventilatory assist applied to a patient by a mechanical ventilator, comprising (a) at least one first detector that detects, during assisted breathing by the patient, the level of ventilatory assist applied by the patient and the mechanical ventilatorThe suction volume V generated by the two_{Assistance of}And an inspiratory volume V contributed by the mechanical ventilator_Ventilation(ii) a (b) Inspiratory assist pressure P generated by a mechanical ventilator_VentilationThe sensor of (1); (c) pressure P_VentilationAnd volume V_{Assistance of}A first calculator of a first relationship therebetween; (d) pressure P_VentilationAnd volume V_VentilationA second calculator of a second relationship therebetween; (e) a third calculator for a plurality of volumes V_VentilationAnd V_{Assistance of}Which calculates the volume V using the first and second relations_VentilationPressure P of_VentilationWith volume V_{Assistance of}Pressure P of_VentilationIn which volume V_VentilationEqual to volume V_{Assistance of}(ii) a (f) Let P_VentilationThe value is multiplied by the corresponding calculated ratio to calculate the predicted suction pressure P_PredictionAnd volume V_{Assistance of}A multiplier of a third relationship therebetween; and (g) a controller of a mechanical ventilator that controls the level of ventilatory assist using the third relationship.

According to a third aspect, there is provided an apparatus for controlling the level of ventilatory assist applied to a patient by a mechanical ventilator, comprising (a) at least one first detector that detects, during assisted breathing by the patient, an inspiratory volume V produced by both the patient and the mechanical ventilator_{Assistance of}And an inspiratory volume V contributed by the mechanical ventilator_Ventilation(ii) a (b) Inspiratory assist pressure P generated by a mechanical ventilator_VentilationThe sensor of (1); (c) at least one processor; and a memory coupled to the processor and comprising non-transitory instructions that, when executed, cause the processor to: pressure P_VentilationAnd volume V_{Assistance of}A first calculator of a first relationship therebetween; pressure P_VentilationAnd volume V_VentilationA second calculator of a second relationship therebetween; for a plurality of volumes V_VentilationAnd V_{Assistance of}Calculating the volume V using the first and second relationships_VentilationPressure P of_VentilationWith volume V_{Assistance of}Pressure P of_VentilationA third calculator of a ratio of V, wherein_VentilationEqual to volume V_{Assistance of}(ii) a And let P_VentilationThe value is multiplied by the corresponding calculated ratio to calculate the predicted suction pressure P_PredictionAnd volume V_{Assistance of}A multiplier of a third relationship therebetween; and (d) a controller of a mechanical ventilator that controls the level of ventilatory assist using the third relationship.

The foregoing and other objects, advantages and features of the present disclosure will become more apparent upon reading of the following non-limiting description of illustrated embodiments, given by way of example only, and with reference to the accompanying drawings.

Drawings

In the drawings:

FIG. 1 is a graph showing the electrical activity profile of a patient's diaphragm during inspiration for a patient with mechanical ventilatory assist (assisted breathing) and during inspiration for a patient without mechanical ventilatory assist (non-assisted breathing);

FIG. 2 is a graph showing a plot of inspiratory volume produced by both the patient and the mechanical ventilator during assisted breathing, a plot of inspiratory volume produced by the patient only during non-assisted breathing, and a plot of the difference in inspiratory volume between assisted and non-assisted breathing (which represents the contribution of the mechanical ventilator to the inspiratory volume during assisted breathing);

FIG. 3 is a graph showing the mechanical ventilatory assist pressure (P) delivered by a ventilator on the x-axis using proportional pressure assist of different gain levels for assisted breathing of a patient_Ventilation) And on the y-axis the inspiratory volume (V) produced by both the patient and the ventilator_{Assistance of}) A graph of (a);

FIG. 4 is a graph showing a representation of a mechanical ventilator (P) on the x-axis when proportional pressure assist is used at different gain levels as shown in FIG. 3_Ventilation) Delivered mechanical ventilatory assist pressure and representation by ventilator (V) on the y-axis_Ventilation) The resulting inspiratory volume (i.e., the inspiratory volume (V) produced by both the ventilator and the patient for the same two assisted breaths (inhalations) as shown in FIG. 3_{Assistance of}) Minus the inspiratory volume (V) generated by the patient alone_{Non-auxiliary}) A chart of);

FIG. 5 is a graph including a first curve and a second curveA graph of two curves, the first curve showing the resulting ventilator pressure/volume relationship (P) obtained using a method similar to that shown in FIGS. 1-4_VentilationRelative V_Ventilation) And the second curve shows the pressure required by the respiratory system to obtain a certain lung volume during paralysis of the respiratory muscles;

fig. 6 is a graph including the following curves: a plot of ventilator assist pressure versus volume produced by both the patient and the ventilator, a plot of ventilator assist pressure versus volume produced by the ventilator alone, and a plot of extrapolated ventilator assist pressure versus volume produced by both the patient and the ventilator;

FIG. 7 is a graph showing plots of inspiratory volume (y-axis) for a patient with no assisted respiration versus electrical activity of the diaphragm EAdi (x-axis) for the patient with no assisted respiration;

FIG. 8 shows P at a matching inspiratory volume_Prediction(y-axis) relative EAdi_{Non-auxiliary}Graph of the curves (x-axis).

Fig. 9 is a block diagram of a ventilatory assist level control apparatus according to one embodiment.

Fig. 10 is a flow chart of a method of ventilatory assist level control according to one embodiment. And

fig. 11 is a simplified block diagram of an example configuration of hardware components that make up the ventilatory assist level control method and apparatus.

Detailed Description

The ventilatory assist level control apparatus 900 and method 1000 will be described with simultaneous reference to fig. 9 and 10.

Referring to fig. 9 and 10, a patient 901 is connected to a mechanical ventilator 902 to receive ventilatory assist. For example, a patient 901 is intubated through a suitable tube 903 and connected to a mechanical ventilator 902. Alternatively, the cannula may be replaced with a respiratory mask (not shown) through which ventilation assistance from a mechanical ventilator 902 is provided to the patient 901. Specifically, as described in U.S. patent 5,820,560 (the entire contents of which are incorporated herein by reference), the mechanical ventilator 902 includes a system (not shown) for supplying breathable gas to a patient 901 through a tube 903 and an intubation tube or respiratory mask.

The mechanical ventilator 902 is controlled by a controller 904. The controller 904 may be integrated into the mechanical ventilator 902 or provided as a separate unit. Also, ventilatory assist level control 900 may be integrated into controller 904 or provided as a separate unit.

In the ventilatory assist level control apparatus 900 and method 1000, the controller 904 may be based on a so-called NAVA (neuromodulation ventilatory assist) mechanical ventilatory assist mode, as described in us patent 5,820,560. The NAVA not only synchronizes operation of the mechanical ventilator 902 with the patient's inspiratory effort (effort), but also controls the mechanical ventilator 902 to deliver a positive ventilatory assist pressure that is proportional to the electrical activity of the patient's respiratory muscles, such as the patient's diaphragm electrical activity (EAdi). In particular, the magnitude of the pressure assist provided to the patient 901 by the mechanical ventilator 902 is regulated by a gain factor that converts the electrical activity of the patient's respiratory muscles (e.g., EAdi) to an assist pressure level; this gain factor is the so-called NAVA level. Of course, it is within the scope of the present disclosure to use electrical activity of the respiratory muscles other than the patient's diaphragm. Likewise, it is within the scope of the present disclosure to use physiological signals similar to electrical activity EAdi.

To make parameter measurements during non-assisted breathing, the controller 904 commands the mechanical ventilator 902 to not provide ventilatory assist during that breath (non-assisted breathing). The controller 904 then signals the corresponding sensor/detector that the current breath is a non-assisted breath. Data from a large number of non-assisted breaths can be stored to better represent such data.

In the same manner, the controller 904 signals the sensor/detector when the current breath is a assisted breath (i.e., a breath during which the mechanical ventilator 902 provides ventilatory assist to the patient).

Measuring EAdi (EAdi) during non-assisted breathing_{Non-auxiliary}) In operation 1005, the EAdi detector 905 measures EAdi_{Non-auxiliary}. In the same manner, the EAdi detector 905 measures EAdi (EAdi) during assisted breathing in operation 1006 (operation of measuring EAdi during assisted breathing)_{Assistance of}). Also, it should be noted that use is made of a diaphragm other than the patientOther electrical activities of the respiratory muscles are within the scope of the present disclosure.

As described in U.S. patent 5,820,560, the EAdi detector 905 may comprise an array of electrodes mounted on an oesophageal catheter which passes through the centre of a patient's diaphragm depolarization region. The center position of the diaphragm depolarization region of the patient is determined by the reversal of the polarity of the electromyogram component of the electromyogram signal detected by the detection electrode. First and second electromyographic signals detected by electrodes of the array on opposite sides of a patient's diaphragm depolarization area are subtracted from each other, the subtraction cancelling noise components of the first and second electromyographic signals but summing together respective electromyographic components of these first and second signals to produce an electromyographic signal (EAdi) having an improved signal-to-noise ratio, having reduced filtering effects caused by electrode position, and representing a need for excitation from the patient's brain.

Fig. 1 is a graph showing a plot 101 of an example of EAdi measured during inspiration of a patient with mechanical ventilation assistance (also referred to as "assisted breathing"), and a plot 102 of a subsequent example of EAdi measured during inspiration of a patient without mechanical ventilation assistance (also referred to as "non-assisted breathing");

to simplify the model, assisted and non-assisted breathing with similar EAdi waveforms is shown in fig. 1. Specifically, both assisted and non-assisted breathing use the same neural recruitment, and will provide similar inspiratory muscle force generation, except for a reduction in the speed and length-tension of some muscle functions caused by an increase in flow (flow) and volume during assisted breathing.

In an operation 1007 of measuring the inspiratory volume of a patient during non-assisted breathing, a spirograph 907 (detector) measures the inspiratory volume V during non-assisted breathing_{Non-auxiliary}. In the same manner, in an operation 1008 of measuring the inspiratory volume of the patient during assisted breathing, the spirograph 907 measures the inspiratory volume V during the assisted breathing_{Assistance of}. It is within the scope of the present disclosure to implement at least one volume/flow detector other than a spirograph.

FIG. 2 is a diagram showing the assistance of a patientInspiratory volume V generated by both patient and mechanical ventilator measured during assisted breathing_{Assistance of}And a curve 202 of the inspiratory volume generated by the patient only, measured during non-assisted breathing of the patient. The difference in inspiratory volume between assisted and non-assisted breathing represents the contribution V of the mechanical ventilator 902 to the inspiratory volume during assisted breathing_Ventilation(curve 203).

Since fig. 1 shows two breaths with similar nerve recruitment, one is assisted (curve 101) and the other is not (curve 102), which functionally means that the inspiratory volume produced by both the patient and the mechanical ventilator and measured during the assistance (fig. 2, curve 201) will be larger than the inspiratory volume produced by the patient only and measured during the non-assisted breathing (fig. 2, curve 202). Thus, the inspiratory volume difference between the assisted breathing and the non-assisted breathing calculated by the subtractor 909 in operation 1009 represents the contribution V of the mechanical ventilator 902 to the patient's inspiratory volume_Ventilation(FIG. 2, curve 203):

V_ventilation＝V_{Assistance of}-V_{Non-auxiliary}(1)

Wherein V_VentilationIs the inspiratory volume, V, of the patient contributed by the mechanical ventilator 902_{Assistance of}Is the inspiratory volume produced by both the patient and the ventilator during assisted breathing of the patient, and V_{Non-auxiliary}Is the inspiratory volume of the patient that is generated by the patient only during non-assisted breathing.

In the same manner, in an operation 1010 of measuring inspiratory flow of a patient during non-assisted breathing, the spirograph 907 measures inspiratory flow F during non-assisted breathing_{Non-auxiliary}. In the same manner, in an operation 1011 of measuring inspiratory flow of a patient during assisted breathing, the spirograph 907 measures inspiratory flow F during assisted breathing_{Assistance of}。

The difference in inspiratory flow between assisted and non-assisted breaths is calculated in operation 1012 by subtractor 912. At the assistant (F)_{Assistance of}) And non-auxiliary (F)_{Non-auxiliary}) The difference in inspiratory flow during breathing provides the inspiratory flow F produced by the mechanical ventilator alone_Ventilation：

F_Ventilation＝F_{Assistance of}-F_{Non-auxiliary} (2)

The controller 904 may use the inspiratory flow value F_Ventilation、F_{Assistance of}And F_{Non-auxiliary}To control the inspiratory flow provided by the mechanical ventilator 902 to the patient 901 in relation to the ventilatory assist mode used.

It should be noted that all calculations are based on similar EAdi amplitude levels during assisted and non-assisted breathing. If the EAdi level is not appropriate, the disparity in EAdi level between assisted and non-assisted breathing needs to be compensated. For example, data stored for a large number of non-assisted breaths may be used to determine and use an average of EAdi levels.

Obtaining a respiratory system pressure versus volume curve, respiratory system mechanical characteristics, patient relative pressure contribution for inspiration

Measuring a mechanical ventilatory assist pressure P delivered to a patient 901 by a mechanical ventilator 902_VentilationIn operation 1013, the pressure sensor 913 measures the mechanical ventilatory assist pressure P_Ventilation. The pressure sensor 913 is typically integrated into the mechanical ventilator 902, but other types of arrangements are possible. Examples of pressure sensors are diaphragm pressure sensors, differential pressure sensors, and the like. By way of non-limiting example, a diaphragm pressure sensor may include a metal diaphragm with a piezometer incorporated thereon. The diaphragm is subjected to the pressure of the gas to be measured and the piezometer senses the deformation of the diaphragm metal caused by the gas pressure to provide a measurement of that pressure. Of course, other types of pressure sensors may be employed.

In operation 1014, the calculator 914 calculates a mechanical ventilation assistance pressure P_VentilationAnd a suction volume V_{Assistance of}By establishing a mechanical ventilatory assist pressure P, for example_VentilationRelative volume of inspiration V_{Assistance of}Curve (c) of (d). Fig. 3 shows on the x-axis the mechanical ventilatory assist pressure P delivered by the ventilator for two assisted breaths (inspiration)_VentilationAnd on the y-axis the inspiratory volume V produced by both the patient and the ventilator_{Assistance of}Using proportional pressure assistance with different gain levels; curve 301 is associated with a higher gain level (NAVA level of 3.0) and curve 302 is associated with a lower gain level (1/3)^rd) The gain level (NAVA level of 0.9) is correlated.

In operation 1015, the calculator 915 calculates the mechanical ventilatory assist pressure P_VentilationWith suction volume V_VentilationIn relation to each other, e.g. by establishing a pressure P_VentilationRelative volume of inspiration V_VentilationCurve (c) of (d). In the graph of fig. 4, the mechanical ventilatory assist pressure P delivered by the mechanical ventilator is represented on the x-axis for the same two breaths (inhalations) as shown in fig. 3_VentilationAnd on the y-axis the inspiratory volume V generated by the ventilator_Ventilation(i.e. the inspiratory volume V generated by both the ventilator and the patient_{Assistance of}Subtracting the inspiratory volume V generated by the patient alone_{Non-auxiliary}) The same proportional pressure assist of different gain levels (NAVA levels) as shown in fig. 3 is used.

In fig. 3, the two curves 301 and 302 are different, since the patient's contribution to the inspiratory pressure and volume is unknown. In fig. 4, curves 401 and 402 overlap because the patient's pressure contribution is removed and the mechanical ventilator pressure contribution P is removed_VentilationIs the only pressure to overcome the patient respiratory system load to create the inspiratory volume.

Fig. 5 shows the results of the experiment in rabbits. Curve 502 illustrates the resulting ventilator pressure/volume relationship (P) obtained using a method similar to that shown in FIGS. 1-4_VentilationRelative V_Ventilation). In particular, curve 502 represents the pressure required by the patient's respiratory system to achieve a given patient's lung volume. For reference, curve 501 defines the pressure/volume curve obtained during post-paralysis volume-controlled ventilation in the same experiment with the same inspiratory flow as during spontaneous breathing.

As shown in FIG. 5, subtracting the inspiratory volume produced by the patient's inspiratory muscle defines a pressure/volume curve 502 (P)_VentilationRelative V_Ventilation) Its shape is similar to the pressure/volume curve 501 of controlled mode ventilation during paralysis and therefore represents the relaxed pressure/volume curve of the respiratory system.

Due to the auxiliary level control of ventilationApparatus and method based on inspiratory volume V from assisted breathing_{Assistance of}Subtracted by the inspiratory volume V of non-assisted breathing_{Non-auxiliary}The resulting volume value will therefore be reduced, e.g. V unless the ventilation assistance overcomes 100% of the patient's respiratory system load_VentilationThe end-inspiration volume cannot be reached. The following description explains how to extend the pressure/volume curve and predict the value of the entire inspiration during partial ventilatory assist.

The increase in EAdi is proportional to the increase in inspiratory muscle contraction, lung inflation pressure and lung volume, however, the length-tension relationship of the diaphragm has some effect on volume (chest wall architecture). For its configuration, the patient increases EAdi proportionally by the EAdi controlled proportional ventilation assist system (or other pressure delivered system proportional to inspiratory effort) to increase the patient and ventilator pressures/forces to inflate the lungs. Thus, the EAdi: 1) increasing the respiratory system expansion pressure/force of the patient and ventilator to produce a volume and 2) proportionally changing the respiratory system expansion pressure/force of the patient and ventilator.

Furthermore, for any given level of EAdi (or other measure of neurological effort), the ventilatory assist from a mechanical ventilator may be varied by adjusting a gain that determines the amount of ventilator-generated pressure that a certain level of EAdi should produce, for example, as described in U.S. patent 5,820,560. This gain adjustment is performed by changing the so-called NAVA level using NAVA (neuromodulation ventilatory assist), as described, for example, in Sinderby c., Navalesi p., Beck j., Skrobik y.comosis n., Friberg s., Gottfried s.b., Lindstrom l, "Neural Control of Mechanical ventilation in Respiratory Failure," Nature Medicine, vol.5(12): pp 3-1436,1999, 12, the entire contents of which are incorporated herein by reference. Conversely, the efficiency with which a patient generates a pulmonary distention pressure for a given EAdi cannot be adjusted, but may vary depending on the physiological or pathophysiological factors of the patient.

Due to the architecture of the human physiology and the proportional assisted ventilation system, the increased respiratory drive (e.g., EAdi) has a similar effect on the chest wall and lung inflation pressures/forces of the patient and ventilator, with different relative contributions depending on the patient's neuromechanical efficiency (NME) and gain settings for proportional assistance (e.g., NAVA levels). NME is defined as the efficiency of the patient's respiratory system to generate inspiratory pressure in response to the electrical activity (EAdi) of the patient's diaphragm.

From the above reasoning, it follows that the increased (figure 3) positive pressure P generated by a proportional assisted ventilator throughout inspiration_VentilationMust be mirrored (proportional) by the increased negative lung inflation pressure generated by the patient's respiratory muscles. Once the volume contribution of the patient is subtracted (FIG. 4), it can be determined by the patient and the ventilator (V)_{Assistance of}Fig. 6, curve 601) and ventilator alone (V)_Ventilation) (i.e., subtracting the volume generated by the patient) (fig. 6, curve 602) yields a matching inspiratory volume, the ventilator's supplemental pressure P is compared_VentilationThe value is obtained.

The graph of fig. 6 represents the ventilator's auxiliary pressure P on the x-axis_VentilationThe volume (V) produced by both the patient and the ventilator is expressed relatively on the y-axis_{Assistance of}Curve 601) and volume (V) generated by a separate ventilator_VentilationCurve 602). Curve 603 shows the curve adjusted to match V_VentilationCurve 602 of the ventilator's auxiliary pressure P_Ventilation. The predicted P_VentilationExtension (extrapolation) of the values to a higher volume V_VentilationThe volume up to the end of inspiration, subsequently called P_Prediction. Predicted pressure P_PredictionIt can be simply calculated as follows.

In operation 1016, the calculator 916 determines that the same inspiratory volume V is present_VentilationAnd V_{Assistance of}Lower ventilator auxiliary pressure P_VentilationThe ratio between the values. P from curve 601 of FIG. 6 may be used_Ventilation(in volume V)_{Assistance of}Lower) value and P from fig. 4_Ventilation(in volume V)_VentilationLower) value. Specifically, the calculator 916 calculates the following ratio:

P_ventilation(V_Ventilation)/P_Ventilation(V_{Assistance of}) In which V is_Ventilation＝V_{Assistance of} (3)

From the example of FIG. 6, V_VentilationIs P at 84ml_Ventilation(7.4cm H₂O) (Curve 603) divided by V_VentilationIs P at 84ml_Ventilation(3.2cmH₂O) (curve 601) equals a ratio of 2.3. For a plurality of inspiratory volumes V_VentilationAnd V_{Assistance of}The ratio of equation (3) is calculated.

In operation 1017, the multiplier 917 adds P_VentilationThe value is multiplied by the corresponding ratio of equation (3) to calculate the predicted pressure P_PredictionAnd a suction volume V_{Assistance of}In relation to each other, e.g. by establishing a predicted pressure P_PredictionRelative volume of inspiration V_{Assistance of}Curve (c) of (d). When compared to the inspiratory volume V_{Assistance of}When plotted (FIG. 6, curve 603), the predicted pressure P_PredictionA pressure/volume curve of the patient's respiratory system is provided for the entire inhalation.

P at calculated VT (VT-tidal volume)_PredictionIn operation 1018, the calculator 918 uses the curve 603 of FIG. 6 to determine the pressure assist, P, required to generate the tidal volume VT_Prediction@ VT. Tidal volume is the lung volume, representing the normal air volume between normal inhalation and exhalation without additional effort; the tidal volume may be measured using, for example, a spirograph 907. The curve fitting method may be used for extrapolation to obtain pressure values at higher inspiratory volumes than the patient's spontaneously generated volume.

Controller 904 may use the pressure required by the patient to generate tidal volume, i.e., P, in any proportional or non-proportional ventilatory assist mode_Prediction@ VT to determine the rate or percentage of pressure assist delivered relative to the desired pressure.

As shown in FIG. 6, P_VentilationAnd P_PredictionCan be in any inspiratory volume V_{Assistance of}Obtained as follows. Thus, in calculating the pressure P generated by the patient_{Patient-prediction}In operation 1019, the subtractor 919 subtracts from V at the same volume_{Assistance of}P of_PredictionMinus P_VentilationTo provide a pressure P generated by the patient_{Patient-prediction}：

P_{Patient-prediction}＝P_Prediction-P_Ventilation (4)

Then, the patient contribution to the inspiratory pressure is calculated as% P_{Patient's health}In operation 1020 at% VT, calculator 920 solves the following equation:

P_{patient's health}％VT＝(P_{Patient-prediction}/P_Ventilation)X 100 (5)

P can be used at any inspiratory lung volume_{Patient-prediction}And P_VentilationCalculate equation 5, including VT (P) at the end of inspiration_{Patient's health}％VT)。

Controller 904 may use the inspiratory flow value P_{Patient-prediction}And P_{Patient% VT}To control the inspiratory pressure applied to the patient 901 by the mechanical ventilator 902 in relation to the configuration of the ventilatory assist mode being used.

P of FIG. 6_VentilationRelative V_VentilationCurve 602 and P_PredictionRelative V_{Assistance of}Curve 603 of (a) shows the pressure required to expand the entire respiratory system to a lower volume or the entire assisted inspiration, respectively. The end-inspiratory portion of the curve (flow near zero) describes the dynamic compliance of the overall respiratory system (expressed as, e.g., ml/cmH₂O) or elastic (described, for example, as cmH)₂O/ml). Actual P_PredictionRelative V_VentilationWill allow the calculation of the respiratory mechanics within the breath. Methods for calculating compliance or elasticity from inspiratory pressure/volume curves are numerous and well described in the literature. Positive End Expiratory Pressure (PEEP) may be included or subtracted depending on the intended application.

Make the mechanical respirator at different inspiration volumes V_VentilationLower generation of suction flow F_VentilationAnd the predicted pressure P_PredictionInspiratory airflow resistance (e.g., described as cmH) may be calculated₂O/ml/s). Methods of calculating the resistance from the continuously recorded suction pressure, flow and volume are also numerous and described in the literature.

Likewise, the value of this dynamic compliance or elastance of the overall respiratory system and inspiratory flow resistance may be used by controller 904 to control the ventilatory assist provided to patient 901 by mechanical ventilator 902 in relation to the configuration of the ventilatory assist mode used.

Obtaining EAdi associated with desired EAdi without auxiliary moisture volume

As described above, in operation 1006, EAdi is measured during the first breath with ventilatory assist_{Assistance of}And in operation 1005, measuring EAdi during a second breath without ventilatory assist_{Non-auxiliary}. The EAdi trajectories for the two breaths were similar as shown in FIG. 1. Inspiratory volume V of the patient + ventilator contribution during the first assisted breath_{Assistance of}And during a second non-assisted breath only the inspiratory volume V of the patient (operation 1008)_{Non-auxiliary}Is also available (operation 1007).

In operation 1021, the electrical activity EAdi of the diaphragm required by the patient to produce the tidal volume VT is determined by the calculator 921_Prediction@ VT. FIG. 7 is a graph showing inspiratory volume V of respiration for a patient without ventilatory assist_{Non-auxiliary}(y-axis) electrical activity EAdi relative to the diaphragm for unassisted breathing_{Non-auxiliary}Graph of the curves (x-axis). In particular, curve 701 represents the electrical activity of the diaphragm EAdi during non-assisted breathing for a given patient_{Non-auxiliary}Resulting in an inspiratory volume V of the patient_{Non-auxiliary}. Curve 701 allows for any inspiratory lung volume V without ventilatory assist_{Non-auxiliary}Lower estimate EAdi_{Non-auxiliary}. However, during assisted and non-assisted inspiration, EAdi is expected to be similar, and as the NAVA level increases, the inspiratory volume difference between assisted and non-assisted breathing at a given EAdi is expected to decrease. In the case of large volume differences between assisted and non-assisted breathing, the curve fitting method (dashed line 702 in FIG. 7) makes it possible to extrapolate EAdi to obtain the non-assisted inspiratory volume V_{Non-auxiliary}EAdi required to reach VT_Prediction@ VT, i.e., the inspiratory volume or greater observed in curve 603 of FIG. 6, which will provide the estimated EAdi required to reach the auxiliary inspiratory volume (equal to VT) without ventilatory assist.

In operation 1022, the calculator 922 uses EAdi required for the patient to generate the tidal volume VT_Prediction@ VT and EAdi_{Non-auxiliary}To calculate the electrical activity EAdi produced by the patient's respiratory muscles_{Non-auxiliary}Relative to each otherPredicting EAdi required to produce tidal volume in a patient's respiratory muscle_PredictionThe percentage EAdi% VT of @ VT, as using equation (6):

EAdi％VT＝(EAdi_{non-auxiliary}/EAdi_Prediction@VT)X 100 (6)

In fact, the EAdi required by the patient to generate the tidal volume VT_Prediction@ VT may be used in any proportional or non-proportional assist mode to determine the EAdi of electrical activity produced relative to the EAdi required for producing the tidal Volume (VT)_PredictionA ratio or percentage of @ VT. For example, using FIG. 7, EAdi_{Non-auxiliary}About 8 μ V, EAdi_Prediction@ VT is about 12 μ V (EAdi% VT ═ 67%), indicating that the patient produces the electrical activity EAdi required to inhale about 3/4 without assistance.

Determining the neuromechanical effort required to reach inspiratory volume

In operation 1023, the neuromechanical efficiency of the patient's respiratory system (NMERS) is determined by the calculator 923.

At a matching inspiratory lung volume, by obtaining a predicted pressure P as shown_PredictionThe value of (e.g., curve 603 of FIG. 6) and the electrical activity EAdi_{Non-auxiliary}May be calculated as cmH (e.g., from curve 701 of FIG. 7)₂P in O/. mu.V meter_Prediction/EAdi_{Non-auxiliary}The ratio of (a) to (b). Using V_VentilationThe ratio is also calculated using the ratio at a given V_VentilationP of_VentilationAnd the same V_{Non-auxiliary}EAdi at value_{Non-auxiliary}. This ratio describes the amount of pressure required per unit of EAdi to overcome the total respiratory system load, i.e. the neuromechanical efficiency (NMERS) of the patient's respiratory system.

For example, at a lung volume of 200ml, P_Prediction＝12.3cmH₂O (FIG. 6, curve 603) and EAdi_{Non-auxiliary}7.8 μ V (fig. 7, curve 701), the neuromechanical efficiency NMERS of the respiratory system of a patient without ventilatory assist is given_{Non-auxiliary}H is 1.6cm H₂O/. mu.V. This means a moisture volume (V) of 350ml_{Assistance of}) Requires 20cmH₂Pressure P of O_Prediction@ VT (FIG. 6, curve 603), which in turn requires 12.5 μ V of EAdi_Prediction@ VT (drawing)7, curve 702). This is represented by the following equation:

P_prediction@VT/NMERS_{Non-auxiliary}＝EAdi_Prediction@VT (7)

NMERS_{Non-auxiliary}＝P_Prediction@VT/EAdi_Prediction@VT (8)

When P is present_Prediction@VT＝20cmH₂O and NMERS_{Non-auxiliary}＝16cmΗ₂At O/. mu.V, equation (7) gives EAdi_Prediction@ VT ═ 12.5 μ V. This is similar to EAdi of curve 702 in FIG. 7_PredictionThe extrapolated value of @ VT.

FIG. 8 Curve 801 shows P at matching inspiratory volume_Prediction(y-axis) relative EAdi_{Non-auxiliary}(x-axis). Open square 803 represents P_Prediction@ VT (y-axis) relative EAdi_Prediction@ VT (x-axis). The dashed line 802 represents a curve fitting model (in this case a quadratic polynomial) which makes it possible to obtain a mathematical function which corrects the final non-linearity.

Method for determining (gain) level of assistance

Gain factors for proportional assistance are required (i.e. e.g. in cmH)₂NAVA level expressed in O/μ V) delivery ventilation assistance, and the effect of the gain factor may be using neuromechanical efficiency NMERS_{Non-auxiliary}And (4) calculating. For example, matching NMERS is applied_{Non-auxiliary}The NAVA level of (a) will double the inspiratory pressure generation at a given EAdi. For example, 2cmH₂NAVA level and 2cmH of O/. mu.V₂NMERS of O/. mu.V_{Non-auxiliary}Application to patients will result in a neuromechanical efficiency NMERS with ventilatory assist_{Assistance of}Total increase of 4cmH₂O/. mu.V. In operation 1024, the calculator 924 calculates the neuromechanical efficiency NMERS_{Assistance of}：

NMERS_{Assistance of}NAVA level + NMERS_{Non-auxiliary}(9)

After several breaths this should reduce the EAdi (and hence the inspiratory pressure generated by the patient) required to generate the required volume to about half (if the inspiratory volume remains unchanged).

In operation 1025, the calculator 925 calculates the ratio NMERS_{Non-auxiliary}/NMERS_{Assistance of}And NMERS_{Assistance of}/NMERS_{Non-auxiliary}。

Ratio NMERS_{Non-auxiliary}/NMERS_{Assistance of}(%) means breathing from no assistance (NAVA level 0 cmH)₂O/μ V) and the percentage of EAdi decreases with increasing NAVA levels.

In contrast, ratio NMERS_{Assistance of}/NMERS_{Non-auxiliary}Indicating when ventilatory assist is removed (i.e., returning the NAVA level to 0cmH₂O/. mu.v) expected fold increase in EAdi. Specifically, at a given NAVA level, the electrical activity EAdi at the end of inspiration of the non-assisted respiration is multiplied by the ratio NMERS_{Assistance of}/NMERS_{Non-auxiliary}Obtaining EAdi_Prediction@VT。

Therefore, how changes in NAVA levels change EAdi can be predicted from absolute (μ V) and relative (%) values.

FIG. 7 shows EAdi_Prediction@ VT is about 12.5 μ V, while EAdi observed during non-assisted breathing at NAVA levels of 0.9 is about 8 μ V. Discovery of NMERS_{Non-auxiliary}Is 1.6cmH₂O/. mu.V (see above examples) and assuming NMERS_{Assistance of}Is 2.5cmH₂O/μV(NMERS_{Non-auxiliary}/NMERS_{Assistance of}1.6/2.5-0.64). EAdi of 12.5 μ V_PredictionNMERS of @ VT multiplied by 0.64_{Non-auxiliary}/NMERS_{Assistance of}The ratio gives an EAdi of 8.0. mu.V.

According to FIG. 7, EAdi at 7.7. mu.V yields a volume of about 230 ml.

It will be appreciated that the controller 904 may use the above relationships and calculated values to control the mechanical ventilator 902 and, thus, the variable of patient ventilatory assist.

Initial setting of NAVA gain level

In the case where the patient is not assisted, i.e. the patient is not supported by ventilation, an initial arbitrary NAVA level is used which provides, for example, 10-20cmH delivered by a ventilator₂The pressure of O. Simple calculations indicate that EAdi at 20 μ V should reach 20cmH at a NAVA level of 1₂The peak pressure of O. If assistance is sufficient, this should be due to unloading; then a) increase the inspiratory volume and/or b) decrease the EAdi.

If the patient is ventilated using an assist mode other than NAVA, the patient may be transitioned to NAVA ventilatory assist mode using existing and built-in tools. If EAdi is significantly higher than the noise level, the ventilator assist pressure/inspiratory EAdi (cmH) associated with the applied ventilatory assist mode may be estimated₂O/μ V) and this value is used as the initial NAVA level.

Embodiments for simplifying applications

The methods and systems provided above may be modified to accommodate any other mechanical ventilation mode, even if such a mode is not capable of delivering proportional pressure ventilation assistance.

The controller 904 may control the mechanical ventilator 902 using a comparison of inspiratory volumes between assisted breathing and non-assisted breathing using inspiratory volume and EAdi only at one point, e.g. at peak EAdi or peak volume or at matching EAdi or volume or any combination of these. For example, respiration with ventilatory assist gives 400ml of V for EAdi of 10 μ V_{Assistance of}And unaided respiration gives 200ml of V for EAdi of 10 μ V_{Non-auxiliary}. For assisted inspiration, measured ventilator pressure P_VentilationIs equal to 10cmH₂And O. The inspiratory volume of non-assisted breathing (400-200 ml) was subtracted from the inspiratory volume of assisted breathing to bring the ventilator to 10cmH₂Volumes of 200ml were delivered under pressure of O at matching EAdi. In this embodiment, the patient's respiratory system (P)_RS) The volume to pressure ratio of (A) is 20ml/cmH₂O and requires 10 μ V.

Simply assuming that breaths following each other have similar respiratory drive (similar EAdi levels), the inspiratory volume of non-assisted breaths may be subtracted from the inspiratory volume of assisted breaths only and the result divided by the above-mentioned ventilatory assist pressure PEEP.

In this regard, it should be noted that the ventilatory assist level control method 1000 is performed if the peak EAdi difference between non-assisted breathing and assisted breathing as shown in fig. 1 is small, e.g., less than or equal to 20%. However, if the peak EAdi difference between non-assisted and assisted breathing is above 20%, the data is ignored and the calculation is aborted.

Embodiments for controlling a mechanical ventilator

In this embodiment, the target P is_{Patient's health}％T_TargetInput to the controller 904 (fig. 9 and 10). Controller 904 then calculates the patient's contribution to inspiratory pressure P from calculator 920_{Patient's health}% VT and the input target P_{Patient's health}％VT_TargetA comparison is made. If the contribution P of the patient_{Patient's health}% VT equal to or greater than target P_{Patient's health}％VT_TargetThe auxiliary, or NAVA, level is increased. If the contribution P of the patient_{Patient's health}% VT is below target P_{Patient's health}％VT_TargetThe auxiliary, or NAVA, level decreases. The NAVA level may be increased and decreased by predetermined increments and decrements.

At the time of the target P_{Patient's health}％VT_TargetAfter input to the controller 904, the predicted inspiratory pressure P from the calculator 918 is first used_Prediction@ VT and the patient's pressure contribution P from the subtractor 919_{Patient-prediction}Calculate a new NAVA level from the total pressure required to reach the tidal volume VT, resulting in the patient's contribution to inspiratory pressure P at the tidal volume VT from calculator 920_{Patient's health}% VT. These measurements are combined with EAdi from calculator 921_Prediction@ VT is related to EAdi% VT from calculator 922. Using these values to calculate the non-aided neuromechanical efficiency NMERS_{Non-auxiliary}And with an auxiliary neuromechanical efficiency NMERS_{Assistance of}。

The following are numerical embodiments of calculations that may be performed by the controller 904. For example, if P_{Patient's health}% VT is 50% and P_Prediction@ VT is 30cmH₂O, then P_{Patient-prediction}Is 15cmH₂And O. In this example, if EAdi_Prediction@ VT is 10 μ V, and NMERS can be estimated_{Assistance of}Is 30cmH₂O/10. mu.V, which is NMERS_{Non-auxiliary}Since P is input to the controller 904 at a 50% value_{Patient's health}％VT_Target. NAVA level equal to NMERS_{Assistance of}Minus NMERS_{Non-auxiliary}I.e. NAVA level equal to (30 cmH)₂O/10μV-15cmH₂O/10μV)/10＝1.5cmH₂O/. mu.V, where division by 10 means division by EAdi_Prediction@ VT. The controller 904 then monitors and analyzes the signal P from the calculator 921_{Patient's health}% VT, EAdi% VT from calculator 922 and ratio NMERS from calculator 925_{Assistance of}/NMERS_{Non-auxiliary}To verify the NAVA level of the value, for example by determining whether the signals have an expected value or range of values, otherwise the ventilator will trigger an alarm. Especially if P_{Patient's health}% VT vs. target P_{Patient's health}％VT_TargetOtherwise, the NAVA level is modified as described above until the target P is reached_{Patient's health}％VT_Target。

If, subsequently, the patient is able to breathe himself, P_{Patient's health}％VT_TargetSet to 75% and P_Prediction@ VT is still 30cmH₂O，P_{Patient-prediction}Then it is 22.5cmH₂And O. In this embodiment, EAdi_Prediction@ VT is still 10 μ V. NMERS_{Assistance of}Then it is 30cmH₂O/10 μ V, NMERS for neuromechanical efficiency_{Non-auxiliary}1.33 times of. NMERS_{Assistance of}Then it is 30cmH₂O/10 μ V and NAVA level equal to NMERS_{Assistance of}Minus NMERS_{Non-auxiliary}I.e., (30 cmH)₂O/10μV)-(22.5cmH₂O/10μV))/10＝0.75cmH₂O/. mu.V, divided by 10 means divided by EAdi_Prediction@VT。

Controller 904 continues to monitor and analyze signal P from calculator 921_{Patient's health}% VT, EAdi% VT from calculator 922 and ratio NMERS from calculator 925_{Assistance of}/NMERS_{Non-auxiliary}For example by determining whether these signals have expected values or value ranges, otherwise the ventilator will trigger an alarm. Also, if P_{Patient's health}% VT vs. target P_{Patient's health}％VT_TargetOtherwise, the NAVA level is modified as described above until the target P is reached_{Patient's health}％VT_Target. In addition, the values of these signals will show whether the patient is able to tolerate and adapt to the lower value of the NAVA level (0.75) and the distance the patient is from being able to breathe spontaneously.

Of course, other types of control or ventilatory assist modes using the mechanical ventilator 902 in the controller 904 that employ any values measured and calculated according to the present disclosure are also within the scope of the present invention.

Fig. 11 is a simplified block diagram of an example configuration of hardware components that make up the ventilatory assist level control apparatus and method described above.

A ventilatory assist level control apparatus and method (identified as 1100 in fig. 11) comprises an input 1102, an output 1104, a processor 1106, and a memory 1108.

Input 1102 is configured to receive EAdi, ventilator pressure, inspiratory volume, and inspiratory flow measurements. The output 1104 is configured to provide the above-described calculated data that can be used by the controller 904 to control the mechanical ventilator 902. The input 1102 and output 1104 may be implemented in a common module, such as a serial input/output device.

The processor 1106 is operatively connected to the input 1102, the output 1104, and the memory 1108. Processor 1106 is implemented as one or more processors executing code instructions to support the functions of the various modules of the ventilatory assist level control apparatus and method as shown in figures 9 and 10.

The memory 1108 may include a non-transitory memory for storing code instructions executable by the processor 1106 (specifically, a processor-readable memory including non-transitory instructions) that, when executed, cause the processor to perform: the modules of the ventilatory assist level control apparatus 900 (fig. 9) and the operations of the ventilatory assist level control method 1000 (fig. 10) as described in this disclosure. Memory 1108 may also include random access memory or buffers for storing intermediate processing data from the various functions performed by processor 1106.

Those of ordinary skill in the art will realize that the description of the ventilatory assist level control apparatus and methods is exemplary only and is not intended to be in any way limiting. Other embodiments will readily suggest themselves to such skilled persons having the benefit of this disclosure. Furthermore, the disclosed devices and methods can be customized to provide a valuable solution to the existing needs and problems of controlling mechanical ventilatory assist.

For the sake of clarity, not all of the routine features of the implementations of ventilatory assist level control apparatus and methods are shown and described. It will, of course, be appreciated that in the development of any such actual implementation of the apparatus and method, numerous implementation-specific decisions may be made to achieve the developers' specific goals, such as compliance with application, system, network, and business-related constraints, which will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that the development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art of controlling mechanical ventilatory assist.

In accordance with the present disclosure, the modules, processing operations, and/or data structures described herein may be implemented using various types of operating systems, computing platforms, network devices, computer programs, and/or general purpose machines. Further, those of ordinary skill in the art will recognize that less general purpose devices, such as hardwired devices, Field Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), or the like, may also be used. Where a method comprising a series of operations is implemented by a processor, computer, or machine, the operations may be stored as a series of readable non-transitory code instructions for the processor, computer, or machine, which may be stored on a tangible and/or non-transitory medium.

The modules of the ventilatory assist level control apparatus and methods as described herein may comprise software, firmware, hardware, or any combination of software, firmware, or hardware suitable for the purposes described herein.

In the ventilatory assist level control methods as described herein, the various operations may be performed in various sequences, and some operations may be optional.

Although the present invention has been described above by way of non-limiting, exemplary embodiments thereof, these embodiments may be modified within the scope of the appended claims without departing from the spirit and nature of the invention.

Claims (30)

1. A device for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator, comprising: at least one first detector adapted to measure the inspiratory volume VAssist produced by both the patient and the mechanical ventilator during patient- _assisted breathing; A subtractor adapted to calculate the inspiratory volume V _ventilation contributed by the mechanical ventilator; a sensor adapted to sense the inspiratory assist pressure P _ventilation produced by the mechanical ventilator; a first calculator of a first relationship between pressure _Pventilation and volume _Vassist ; a second calculator of a second relationship between pressure _Pventilation and volume _Vventilation ; A third calculator, for a plurality of volumes _Vventilation and _Vassist , which uses the first and second relationships to calculate the ratio between the pressure _{Pventilation at volume Vventilation and} the pressure _Pventilation at volume _Vassistance , where volume _Vventilation is equal to the volume V _auxiliary ; a multiplier that calculates a third relationship between the _predicted inspiratory pressure _Ppredicted and the volume Vassist by multiplying the _Pventilation value by the corresponding calculated ratio; and A controller of a mechanical ventilator that uses the third relationship to control the level of ventilatory assistance. 2. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 1, wherein, A first calculator constructs a first curve of pressure P _ventilation versus volume V _assist ; A second calculator constructs a second curve of pressure P _ventilation versus volume V _ventilation ; The third relationship is a third curve of pressure P _prediction versus V _assist . 3. The apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 1, comprising: A second detector that detects the electrical activity of the respiratory muscles EAdi unassisted during unassisted breathing of the patient and the electrical activity of the respiratory muscles EAdi _assisted during _assisted breathing of the patient. 4. The apparatus for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator of claim 3, wherein the respiratory muscle is the patient's diaphragm. 5. The apparatus of claim 1 for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator, comprising: the at least one first detector that measures the inspiratory volume V _unassisted produced by the patient during unassisted breathing of the patient; and A subtractor that subtracts the volume Vnon _{-assisted from} the volume Vassisted to obtain the inspiratory volume Vventilation contributed by the mechanical _ventilator . 6. The apparatus of claim 1 for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator, comprising: A fourth calculator that uses the third relationship to calculate the _predicted pressure Ppredict at the patient's tidal lung volume. 7. The apparatus for controlling a level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 1, comprising: A subtractor that subtracts the pressure Pventilation from the pressure _{Pprediction assisted} by a given volume V to obtain the patient-contributed inspiratory pressure Ppatient _{-prediction .} 8. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 7, comprising: A fifth calculator that calculates the patient's contribution to the inspiratory pressure at the _patient 's tidal volume, Ppatient %VT, using the following relationship: P _patient %VT = (P _{patient - predicted} /P _ventilation ) x 100. 9. The apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 3, comprising: A fourth calculator that uses an extrapolation, curve fitting technique applied to a curve of electrical activity EAdi _unassisted versus inspiratory volume V _unassisted to calculate the predicted electrical activity EAdi _Predict @VT of the respiratory muscles required by the patient to generate tidal volume. 10. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 9, comprising: A fifth calculator, which calculates the percentage EAdi %VT from the electrical activity EAdi produced by the patient's respiratory muscles _unassisted relative to the predicted electrical activity EAdi _predicted @VT required by the patient's respiratory muscles to produce a tidal volume, using the following relationship: EAdi%VT=(EAdi _unassisted /EAdi _prediction @VT)×100. 11. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 9, comprising: a sixth calculator that uses the third relationship to calculate the _predicted pressure Ppredict@VT at the patient's tidal lung volume VT; and A seventh calculator, for the patient's unassisted breathing, calculates the neuromechanical efficiency of the patient's respiratory system _{NMERS unassisted} as a function of _predicted pressure Ppredict@VT and _predicted electrical activity EAdipredict@VT. 12. An apparatus for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator as claimed in claim 11, comprising: An eighth calculator, for the patient's assisted breathing, calculates the patient's respiratory system neuromechanical efficiency _{NMERS assist} as a function of the neuromodulated ventilatory _assist (NAVA) level and the neuromechanical efficiency NMERS unassisted. 13. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 12, comprising: Calculate at least one of the ratios NMERS _non-assisted /NMERS _assist and NMERS _assist /NMERS _non-assisted . 14. The apparatus of claim 11 for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator, comprising subtracting the pressure at the patient's tidal volume, Pventilation, from the _predicted pressure _Ppredict @VT to obtain a patient-contributed Inspiratory pressure Ppatient _-predicted subtractor, and a calculator that calculates the patient's contribution to inspiratory pressure Ppatient %VT at the _patient 's tidal volume using the following relationship: P _patient %VT = (P _{patient - predicted} /P _ventilation ) × 100 and wherein the controller, Receive target P _patient %VT _target ; Compare the patient's contribution _{Ppatient %VT to the target P patient %} T _target ; and NAVA levels were modified based on comparisons. 15. The apparatus for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator of claim 14, wherein the controller _predicts @VT using predicted pressure P, predicted electrical activity EAdi _predicts @VT and _Patient Contribution to Inspiratory Pressure Ppatient %VT Calculates initial NAVA level. 16. A device for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator, comprising: at least one first detector adapted to measure the inspiratory volume VAssist produced by both the patient and the mechanical ventilator during patient- _assisted breathing; A subtractor adapted to calculate the inspiratory volume V _ventilation contributed by the mechanical ventilator; a sensor adapted to sense the inspiratory assist pressure P _ventilation produced by the mechanical ventilator; at least one processor; and a memory coupled to the processor and including non-transitory instructions that, when executed, cause the processor to perform: a first calculator of a first relationship between pressure _Pventilation and volume _Vassist ; a second calculator of a second relationship between pressure _Pventilation and volume _Vventilation ; A third calculator, for a plurality of volumes _Vventilation and _Vassist , which uses the first and second relationships to calculate the ratio between the pressure _{Pventilation at volume Vventilation and} the pressure _Pventilation at volume _Vassistance , where volume _Vventilation is equal to the volume V _auxiliary ; and a multiplier that calculates a third relationship between the _predicted inspiratory pressure _Ppredicted and the volume Vassist by multiplying the _Pventilation value by the corresponding calculated ratio; A controller of a mechanical ventilator that uses the third relationship to control the level of ventilatory assistance. 17. The device for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator of claim 16, wherein A first calculator constructs a first curve of pressure P _ventilation versus volume V _assist ; A second calculator constructs a second curve of pressure P _ventilation versus volume V _ventilation ; The third relationship is a third curve of pressure P _prediction versus V _assist . 18. The apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 16, comprising: A second detector that detects the electrical activity EAdi unassisted of the respiratory muscles during unassisted breathing of the patient and the electrical activity EAdi _assisted of the respiratory muscles during _assisted breathing of the patient. 19. The apparatus for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator of claim 18, wherein the respiratory muscle is the patient's diaphragm. 20. The apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 16, comprising: the at least one first detector that measures the inspiratory volume V _unassisted produced by the patient during unassisted breathing of the patient; and A subtractor that subtracts the volume Vnon _{-assisted from} the volume Vassisted to obtain the inspiratory volume Vventilation contributed by the mechanical _ventilator . 21. The apparatus for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator as claimed in claim 16, comprising: A fourth calculator that uses the third relationship to calculate the _predicted pressure Ppredict at the patient's tidal lung volume. 22. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 16, comprising: A subtractor that subtracts pressure Pventilation from the pressure _{Pprediction assisted} by a given volume V to obtain the patient-contributed inspiratory pressure Ppatient _{-prediction .} 23. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 22, comprising: A fifth calculator, which calculates the patient's contribution to the inspiratory pressure at the _patient 's tidal volume, Ppatient %VT, using the following relationship: P _patient %VT = (P _{patient - predicted} /P _ventilation ) x 100. 24. The apparatus for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator as claimed in claim 18, comprising: A fourth calculator that uses an extrapolation, curve fitting technique applied to a curve of electrical activity EAdi _unassisted versus inspiratory volume V _unassisted to calculate the predicted electrical activity EAdi _Predict @VT of the respiratory muscles required by the patient to generate tidal volume. 25. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 24, comprising: A fifth calculator, which calculates EAdi %VT percentage, from the electrical activity EAdi produced by the patient's respiratory muscles _unaided relative to the predicted electrical activity EAdi _predicted @VT required to produce tidal volume by the patient's respiratory muscles using the following relationship: EAdi%VT=(EAdi _unassisted /EAdi _prediction @VT)×100. 26. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 24, comprising: a sixth calculator that uses the third relationship to calculate the _predicted pressure Ppredict@VT at the patient's tidal lung volume VT; and A seventh calculator, for the patient's unassisted breathing, calculates the neuromechanical efficiency of the patient's respiratory system _{NMERS unassisted} as a function of _predicted pressure Ppredict@VT and _predicted electrical activity EAdipredict@VT. 27. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 26, comprising: An eighth calculator, for the patient's assisted breathing, calculates the neuromechanical efficiency NMERS _assist of the patient's respiratory system as a function of the neuromodulated ventilatory assist (NAVA) level and the neuromechanical efficiency _{NMERS unassisted} . 28. An apparatus for controlling the level of ventilation assistance applied to a patient by a mechanical ventilator as claimed in claim 27, comprising: Calculate at least one of the ratios NMERS _non-assisted /NMERS _assist and NMERS _assist /NMERS _non-assisted . 29. The apparatus of claim 26 for controlling the level of ventilatory assistance applied to a patient by a mechanical _ventilator , comprising subtracting the pressure P at the patient's tidal volume from the _predicted pressure Ppred@VT to obtain a patient-contributed Inspiratory pressure Ppatient _-predicted subtractor, and a calculator that calculates the patient's contribution to inspiratory pressure Ppatient %VT at the _patient 's tidal volume using the following relationship: P _patient %VT = (P _{patient - predicted} /P _ventilation ) × 100 and wherein the controller, Receive target P _patient %VT _target ; Compare the _patient 's contribution Ppatient %VT to the target _Ppatient %T _target ; and NAVA levels were modified based on comparisons. 30. The apparatus for controlling the level of ventilatory assistance applied to a patient by a mechanical ventilator of claim 29, wherein the controller _predicts @VT using a predicted pressure P, predicted electrical activity EAdi _predicts @VT and the patient Contribution to inspiratory pressure _Ppatient %VT to calculate initial NAVA levels.

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